<script src="../../dist/vue.global.js"></script>
<link rel="stylesheet" href="../../../../node_modules/todomvc-app-css/index.css">

<div id="app">
  <section class="todoapp">
    <header class="header">
      <h1>todos</h1>
      <input class="new-todo"
              autofocus autocomplete="off"
              placeholder="What needs to be done?"
              v-model="state.newTodo"
              @keyup.enter="addTodo">
    </header>
    <section class="main" v-show="state.todos.length">
      <input id="toggle-all" class="toggle-all" type="checkbox" v-model="state.allDone">
      <label for="toggle-all">Mark all as complete</label>
      <ul class="todo-list">
        <li v-for="todo in state.filteredTodos"
            class="todo"
            :key="todo.id"
            :class="{ completed: todo.completed, editing: todo === state.editedTodo }">
          <div class="view">
            <input class="toggle" type="checkbox" v-model="todo.completed">
            <label @dblclick="editTodo(todo)">{{ todo.title }}</label>
            <button class="destroy" @click="removeTodo(todo)"></button>
          </div>
          <input class="edit" type="text"
                  v-model="todo.title"
                  v-todo-focus="todo === state.editedTodo"
                  @blur="doneEdit(todo)"
                  @keyup.enter="doneEdit(todo)"
                  @keyup.escape="cancelEdit(todo)"
          >
        </li>
      </ul>
    </section>
    <footer class="footer" v-show="state.todos.length">
        <span class="todo-count">
          <strong>{{ state.remaining }}</strong>
          <span>{{ state.remainingText }}</span>
        </span>
      <ul class="filters">
        <li><a href="#/all" :class="{ selected: state.visibility === 'all' }">All</a></li>
        <li><a href="#/active" :class="{ selected: state.visibility === 'active' }">Active</a></li>
        <li><a href="#/completed" :class="{ selected: state.visibility === 'completed' }">Completed</a></li>
      </ul>

      <button class="clear-completed" @click="removeCompleted" v-show="state.todos.length > state.remaining">
        Clear completed
      </button>
    </footer>
  </section>
</div>

<script>
const { createApp, reactive, computed, watchEffect, onMounted, onUnmounted } = Vue

const STORAGE_KEY = 'todos-vuejs-3.x'
const todoStorage = {
  fetch () {
    const todos = JSON.parse(localStorage.getItem(STORAGE_KEY) || '[]')
    todos.forEach((todo, index) => {
      todo.id = index
    })
    todoStorage.uid = todos.length
    return todos
  },
  save (todos) {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(todos))
  }
}

const filters = {
  all (todos) {
    return todos
  },
  active (todos) {
    return todos.filter((todo) => {
      return !todo.completed
    })
  },
  completed (todos) {
    return todos.filter(function (todo) {
      return todo.completed
    })
  }
}

function pluralize (n) {
  return n === 1 ? 'item' : 'items'
}

createApp({
  setup () {
    const state = reactive({
      todos: todoStorage.fetch(),
      editedTodo: null,
      newTodo: '',
      beforeEditCache: '',
      visibility: 'all',
      remaining: computed(() => {
        return filters.active(state.todos).length
      }),
      remainingText: computed(() => {
        return ` ${pluralize(state.remaining)} left`
      }),
      filteredTodos: computed(() => {
        return filters[state.visibility](state.todos)
      }),
      allDone: computed({
        get: function () {
          return state.remaining === 0
        },
        set: function (value) {
          state.todos.forEach((todo) => {
            todo.completed = value
          })
        }
      })
    })

    watchEffect(() => {
      todoStorage.save(state.todos)
    })

    onMounted(() => {
      window.addEventListener('hashchange', onHashChange)
      onHashChange()
    })

    onUnmounted(() => {
      window.removeEventListener('hashchange', onHashChange)
    })

    function onHashChange () {
      const visibility = window.location.hash.replace(/#\/?/, '')
      if (filters[visibility]) {
        state.visibility = visibility
      } else {
        window.location.hash = ''
        state.visibility = 'all'
      }
    }

    function addTodo () {
      const value = state.newTodo && state.newTodo.trim()
      if (!value) {
        return
      }
      state.todos.push({
        id: todoStorage.uid++,
        title: value,
        completed: false
      })
      state.newTodo = ''
    }

    function removeTodo (todo) {
      state.todos.splice(state.todos.indexOf(todo), 1)
    }

    function editTodo (todo) {
      state.beforeEditCache = todo.title
      state.editedTodo = todo
    }

    function doneEdit (todo) {
      if (!state.editedTodo) {
        return
      }
      state.editedTodo = null
      todo.title = todo.title.trim()
      if (!todo.title) {
        removeTodo(todo)
      }
    }

    function cancelEdit (todo) {
      state.editedTodo = null
      todo.title = state.beforeEditCache
    }

    function removeCompleted () {
      state.todos = filters.active(state.todos)
    }

    return {
      state,
      addTodo,
      removeTodo,
      editTodo,
      doneEdit,
      cancelEdit,
      removeCompleted
    }
  },

  directives: {
    'todo-focus': (el, { value }) => {
      if (value) {
        el.focus()
      }
    }
  }
}).mount('#app')
</script>
